I have been searching for this for a while, tried suggestions but nothing seemed to work.

So here it is. I have an animation, and I made it at 550px x 400px. I am looking to resize the original .fla file to 1100px by 800px.

People seem to say "try edit multiple frames, onion skin it all and resize all of the frames". Whenever I try this, I have a huge offput of the animation, I believe because resizing the canvas extends right and down, while resizing the animation extends left/right and up/down.

If you want the original movie to display at the larger size, you can just edit the Publish Settings... to have the .swf stretch out to 1100 X 800. If you need to use this existing 550 by 400 movie in another movie at the larger size, you can select the whole existing movie's extent on the main timeline, copy it, create a new empty movieClip, and paste the entire movie into that new movieClip. Then you can open a new movie at 1100 X 800, copy the movieClip into the new movie and resize the clip and position it as you want. Alternately, if you publish an .swf from the original movie, you can load that .swf into a new larger movie and resize the .swf to fit the larger stage.

If you go to the HTML tab in the Publish Settings window, you'll see an option for "Dimensions". It is set to "Match Movie" by default. If you change that to "Pixels", the Width and Height options become available and you can set new values for the size of the Flash movie.

That seems to work for the html, but the SWF stays at 550x400. In this case, is there a way to load the animation off a second flash file that gives an increased animation size? So the SWF is still the same size, but loaded at a larger size.

What you're asking for and what the graphic above does is identical. When you set it to exact fit and specify pixels, your SWF will grow to the size you specify. Exactly as if you loaded the clip into another and then just scaled it up by 2. It will look identical.

Watch out for any code you may have written that may override the HTML, such as:

stage.scaleMode = StageScaleMode.NO_SCALE;

That will keep the SWF from upscaling even though the HTML told it to scale.

You can also be explicit yourself and specify what you want, which is EXACT_FIT:

The browser first needs to load the content. On any modern computer (~5 years or less being very loose) the content should resize instantaneously. If you have a ton of things loading on the first frame it could signal that you need a preloader. How big is the SWF you're loading?

Can you put a sample online somewhere? This would be much easier to diagnose.